Etiology

The primary etiology is believed to be excessive straining due to either chronic constipation or diarrhea. Repetitive or prolonged straining causes downward stress on the vascular hemorrhoidal cushions, leading to the disruption of the supporting tissue elements with subsequent elongation, dilation, and engorgement of the hemorrhoidal tissues.[1][8] Other conditions can contribute to the formation of hemorrhoids: an increase in intra-abdominal pressure can be caused by pregnancy or ascites; the presence of space-occupying lesions within the pelvis may cause a concomitant decrease in vascular return and increase in anal vascular engorgement.[9]

Pathophysiology

Hemorrhoids are a normal anatomic and functional component of the anal canal; they become pathologic and are termed hemorrhoidal disease only when they cause symptoms. As the patient strains at stool, the hemorrhoids are pulled lower into the anal canal. As the vascular cushions engorge, the thin epithelial lining is easily torn, which causes bleeding. This is commonly seen as bright blood on cleansing, but can also be seen in the bowl. The hemorrhoids can enlarge to the point that they protrude from the anal canal and can cause a sensation of incomplete evacuation or require manual reduction following a bowel movement.[1]

External hemorrhoids commonly cause symptoms of pruritus or a feeling of inadequate cleaning following a bowel movement. These hemorrhoidal tissues can also become engorged and clots can form, causing a thrombosed external hemorrhoid. This is commonly preceded by a period of excessive straining. The patient experiences the sudden onset of perianal pain and a tender palpable lesion forms adjacent to the anal canal on the anal margin.

Classification

External hemorrhoids

Hemorrhoids that are located in the distal anal canal, distal to the dentate line, and covered by sensate anoderm or skin.[1]

Internal hemorrhoids (grade 1-4)

Hemorrhoids that originate proximal to the dentate line and are covered by insensate transitional epithelium.

  • Grade 1 - protrusion is limited to within the anal canal.

  • Grade 2 - protrudes beyond the anal canal but spontaneously reduces on cessation of straining.

  • Grade 3 - protrudes outside the anal canal and reduces fully on manual pressure.

  • Grade 4 - protrudes outside the anal canal and is irreducible.

This grading of internal hemorrhoids is only a reflection of the degree of prolapse but is not a measure of either the disease severity or of the size of hemorrhoidal prolapse.[1][2]​​

Use of this content is subject to our disclaimer